Silicon electrostatic nanoelectromechanical systems (NEMS) are one of the emerging applications in nanotechnology. As the critical length of a NEM structure shrinks to less than a few nanometers, classical models based on continuum approximations become inaccurate in predicating the electronic properties of NEM structures. Tight binding approximations (TBA) are typically more accurate in such cases. However, the computational cost involved in solving a TB system constructed using 3D crystal lattice structures (or unit cells) is very high even for small systems. In many NEMS applications, the electronic properties (e.g. the charge density) do not vary in some directions or over a large distance along a particular direction. The application of the classical TB method to model such NEMS applications requires that all the unit cells in all the three directions be taken into account. For typical NEMS examples, this can mean the use of hundreds of thousands of unit cells, which can be practically impossible to model with the classical TB method. If the number of unit cells can be reduced by using the fact that the electronic properties do not vary over a certain direction or over a large distance along a particular direction, then the TB method can be an efficient and accurate approach for electrostatic analysis for NEMS. In this paper, we present a new coarse-grained tight binding approximation (CG-TBA) method, where the key idea is to represent the entire NEM structure with a minimal number of unit cells but to accurately compute the charge density and other electronic properties.
Journal: TechConnect Briefs
Volume: 3, Technical Proceedings of the 2005 NSTI Nanotechnology Conference and Trade Show, Volume 3
Published: May 8, 2005
Pages: 537 - 540
Industry sector: Sensors, MEMS, Electronics
Topic: MEMS & NEMS Devices, Modeling & Applications